Take the system $${\vec{x}\,}'' = \begin{bmatrix} -{\frac{7}{4}} & 1 \\ {\frac{4}{3}} & -{\frac{4}{3}} \end{bmatrix} \vec{x} + \begin{bmatrix} 4 \cos(3 t) \\ 0 \end{bmatrix}$$ Find a particular solution of the form $\begin{bmatrix}x_1(t) \\ x_2(t) \end{bmatrix} = \vec{v} \cos(3 t)$

$x_1(t) = {}$

$x_2(t) = {}$

help (formulas)